Over 1.1 million colorectal cancer (CRC) survivors were alive as of January 2008 and this number continues to grow with the aging of the US population, the early diagnosis of cancer through screening, and the improved effectiveness of colorectal cancer treatments. While there is ample evidence showing that comorbidity affects treatment receipt and survival, little is known about the impact of comorbidity on patient- reported outcomes (PROs) such as disease symptoms, side effects of treatments, and quality of life (QOL) following a diagnosis of cancer. A variety of measures of comorbidity, such as the Charlson Comorbidity Index, the Functional Comorbidity Index, or an enumeration of chronic health conditions, have been used in cancer populations to measure the presence and clinical severity of chronic health conditions but none take into account the impact or burden of existing health conditions on a person's ability to engage in daily activities. A new self-assessment of comorbidity burden, developed by Bayliss and colleagues, assesses over 21 health conditions and the self-assessed impact of each on a person's ability to engage in daily activities. A measure of comorbidity burden may be a better, more informative, predictor of PROs among cancer survivors than currently used measures of comorbidity. The objectives of the proposed study are to evaluate the pre-operative Bayliss measure of comorbidity burden in comparison with other commonly used comorbidity measures on baseline and post-surgery PROs in 200 newly diagnosed CRC patients receiving surgery. We propose the following specific aims: 1. Compare the baseline Bayliss measure of comorbidity burden against commonly used measures of comorbidity with pre-operative PROs of symptoms and QOL among recently diagnosed CRC patients; 2. Compare the baseline Bayliss measure's predictive and discriminative ability for treatment side effects and QOL assessed at: a) 4-6 weeks post-surgery and b) 3 months after surgical treatment; 3. Explore whether specific combinations of pre-operative health conditions are associated with symptoms, treatment side effects, or QOL at 4-6 weeks and 3 months post surgery. We aim to demonstrate that a measure of comorbidity burden explains more of the variation in PROs and better predicts PROs over time than existing comorbidity measures. Findings from this study will inform future selection of comorbidity measures in PRO studies of cancer survivors, address conceptual questions about the associations and predictive ability of comorbidity burden and PROs, and inform the need for clinical and behavioral interventions to improve PROs among cancer survivors with comorbidities.